Ok I need HELP!!!! My 1999 Ranger with a 3.0 V6 is pushing the coolant back into resavoir and out of radiator. The motor is not running hot as the temp gauge stays right in the middle and have checked the sensor and it works fine. So far I have replaced the thermostat twice, replaced radiator,replaced radiator cap, replaced water pump, checked with a pressure test to check for blown head gasket and we started with 8 pounds of pressure and then went to 15 and then 22 pounds of pressure and did not loose any pressure so do not feel it is a head gasket. But why is it doing this I mean I drive down the road the truck runs fine but as soon as I stop and shut it off and pop the hood the coolant resavoir is full and bubbling over and when I turn the radiator cap it has back pressure but radiator looks empty so help has anyone else had this problem and what did you have to do to fix???

The radiator cap is what controls the pressure in the cooling system as well as the flow of coolant to and from the overflow. I know you said that you replaced that but I would suspect that first. Only other thing I can think of that would force coolant out of the system would be a blown head gasket.

[QUOTE=01_ranger_4x4;605964]The radiator cap is what controls the pressure in the cooling system as well as the flow of coolant to and from the overflow. I know you said that you replaced that but I would suspect that first. Only other thing I can think of that would force coolant out of the system would be a blown head gasket.

+1. Take the cap back to the parts store. Get a Motorcraft or a Stant cap. If it continues have a pressure check done on the cooling system to see if you have a head gasket leak. My 93 had a freeze plug pop. When the shop was replacing it they saw a some rust stains on the back of the head. Had both head gaskets replaced.

It could be the cap. But I don't know, I think this sounds a little more extreme than just a cap. The head gasket can be leaking when its hot and not show any symptoms when its cold when you pressure tested it. The cap is cheap and easy so go for it and see what happens.

Well guys it is not the cap I replaced the cap and it continues, When we pressure tested the system it was ran for 30 minutes and brought to normal temp and pump the pressure up to 22 pounds and did not lose any pressure the guage stayed right there the whole time lol so I give up anyone have some cheap dynamite as this piece of crap truck has cost me more than any vehicle I have ever owned and I am old lol!!!

So you're saying you pressure tested the cooling system up to 22 pounds with the engine running and it didn't and warm and it didn't drop? I wouldn't expect it to. Cylinder pressure is a lot more than 22 pounds, pressure wouldn't go down.

I think your head gasket is leaking and that pressure is what's blowing the system out the reserve tank.

Not to be the lone dissenting putz of the group, but I don't instantly agree with the head gasket opinion. The fact that the pressure test is ambiguous leads me to ask a few questions...

- You mention a pressure test. If this is a pressure test of the cooling system alone then you only have half the answer. A proper cylinder compression test should be done to determine if the problem is actually the head gasket or if its something else.

- If the coolant is a correct 50/50 water / ethylene glycol mix and it was a head gasket, would you not smell a sweet note at the exhaust or see a slight amount of moisture in the oil? With that in mind, water spraying into a cylinder would eventually cause a cylinder misfire or a coolant fouled or colored plug.

- To your knowledge has some idiot used Bars Leaks or some other coolant system clogging bullshit in your vehicle? (And has the entire system been properly flushed and refilled per manuf. spec?)

If the engine is operating at correct temperature (which it appears to be..) and all of the other parts are pressure tested, my bet would be on a clogged return line in the coolant system or air bubble that causes the pressure difference that fills the overflow tank when it's not running.

I would approach the problem by getting a compressed air source and "force draining" the system from the highest point. Probably around the thermostat. Some tight rags around an air nozzle until the system is empty. Then do it again a few times with clean water, running it for a few minutes in between cycles..

Refill the system with a 50/50 mix and make sure that there are no "bubbles"... This can take a while as the engine has to get up to running temperature and thermostat full open before all of the air is out of the system. Not real familiar with the 3.0 but I have seen a lot of bleed valves on high spots within the coolant system. If none exist, fill the radiator per the manufacturer spec and warm the engine with the cap off. Once the motor is warm, monitor the radiator level and replace coolant as needed. Make sure to give all the radiator inlet and outlet hoses a squeeze a few times to make sure that there is no air left in the system. Once it stops dropping, seal the new radiator cap.

Take it out and get it hot, run the A/C, etc.... Once home, carefully check the coolant levels. (Even under the cap with a couple of rags..)

If everything looks clean, you should be golden.. If not, I would immediately check for a leak somewhere in the coolant lines that is adding air into the line somewhere... Don't forget about the EGR system as hot water can sometimes run through that as well....

***Disclaimer***

I was a mechanic a long time ago but gave it up for a cushy desk job with great benefits and a secretary with tits that still make me tear up a little.

i have a 2000 3.0 v6 that just hit 100k. it has the same problem, a lot coolant gets pushed out the overflow but it also has redish orange crap in the coolant even after i flushed the whole coolant system. could it be that the tranny fluid cooler inside the radiator burst? I really need help with this one guys.

i have a 2000 3.0 v6 that just hit 100k. it has the same problem, a lot coolant gets pushed out the overflow but it also has redish orange crap in the coolant even after i flushed the whole coolant system. could it be that the tranny fluid cooler inside the radiator burst? I really need help with this one guys.

Yes, absolutely. The transmission runs at a much higher pressure than the cooling system so it will over pressurize the cooling system and eventually draw coolant into the transmission.

Pull the transmission dipstick and see if it looks off. If so, I would stop driving until it is repaired and the transmission is flushed.

Well problem fixed, It was a bad head gasket and while I was at it went ahead and replaced the heads! Dover Cylinder Heads out of Atlanta Georgia has a set of remanufactored heads and with the heads you get a complete set of gaskets and new head bolts for $350 complete and free shipping! Had them in 2 days and best part you do not have to return your old heads back. I live in IL and was going to cost me $150 just to get the old heads checked plus buying the gaskets I would have had $250 in it and used the old heads so for $100 more I have new heads on my truck. The head gasket had a spot where you could clearly see where it had blackened off in that spot. So back on the road with my Ranger and thanks for all the help!!

Some are if you have a bad thermostat, fan clutch, water pump or ECT sensor.

But one overlooked thing can also be why. Water boils at 212 degrees F. If under pressure, it will raise the boiling point.
These systems are under pressure during normal use. If you have a leak in the overflow tank, or elsewhere, it can lower the pressure in the system and cause the water/coolant to boil a bit. Get the pressure back up (new overflow tank) and it will stop.